How do I know if Modbus sensors connected to the PCM are working?
The best source of feedback on the operation of Modbus sensors is the Alarm Log. An alarm “Netwk Comm Errs” or “Network Errors” will be logged if a slave on the network is not responding to inquiries from the PCM. In addition, the “Item” column of the Alarm Log will contain the Slave Number that is reporting the alarm. A Modbus slave will not respond if it’s network address, usually set with switches on the sensor device, is incorrectly sent. The Slave Number of the PCM should correspond with the sensor device’s Modbus address settings (ie Slave 2 should be Modbus address 2). Some Modbus sensors may not respond when an illegal Modbus “register” is being addressed. Consult the sensor’s manual to check that the register values are correctly entered into the PCM’s programming.
